1. Field of the Invention
This invention relates to a multi-chamber positive displacement pump, and in the preferred embodiment of the invention provides a positive displacement pump suitable for delivering high pressure fuel to the fuel injection system of an internal combustion engine. It is to be understood, however, that the invention is not limited to this application and may be utilised in a wide range of multi-chamber positive displacement pumps.
2. State of the Art
Common rail fuel injection systems for internal combustion engines require the provision of a high pressure pump for supplying fuel at high pressure to the common rail or to an accumulator associated therewith. Such pumps must typically operate at pressures up to 1600 bar, and may in the future need to operate at pressures in excess of 2000 bar, and must accordingly be of the positive displacement type. In order to utilise common rail fuel injection technology in mass produced automobile engines the required fuel pump must be effective at delivering the required fuel volume and pressure, but must in addition be highly reliable, compact, and economical to manufacture. The requirements for compact and economical design are particularly difficult to meet in a pump which is required to deliver fuel reliably over many years at the pressures required by common rail fuel injection systems.
Whilst it is generally recognised that reducing the number of individual components in a particular assembly leads to an increase in reliability and a reduction in manufacturing costs, this general desideratum is often at variance with requirements for a compact design and is particularly difficult to achieve in a relatively complex mechanism such as a multi-chamber positive displacement pump.